Variable angle bone plate

ABSTRACT

A bone plate having at least one variable angle locking hole is described. The variable angle locking hole allows a bone anchor having a threaded head to be driven into underlying bone while oriented at an angle with respect to a central hole axis of the hole that is within a range of angles at which the head is configured to threadedly mate with the at least one thread of the bone plate. Accordingly, the bone anchor can be driven into the underlying bone until the threaded head threadedly purchases with the bone plate inside the variable angle locking hole.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims priority to U.S. Provisional PatentApplication Ser. No. 62/385,069 filed on Sep. 8, 2016, the disclosure ofwhich is hereby incorporated by reference as if set forth in itsentirety herein.

BACKGROUND

This disclosure relates generally to bone fixation implants, and inparticular relates to a bone plate that is configured to lockinglyreceive a bone screw at an angular orientation in a range of permissibleangular orientations at which the bone plate can lockingly receive thebone screw.

When bones are damaged through trauma, disease, distractionosteogenesis, or orthognathic surgery, the defect is typically reduced,and bone fixation plates are commonly applied to the bone on oppositesides of the defect to ensure union in the desired position. Bone platesare typically made from a rigid material, such as titanium, and includefixation holes that are sized to be driven through the fixation holesand into the underlying bone to secure the bone plate to the bone. Onecommon bone screw used in such application is generally referred to as acompression screw. Compression screws have unthreaded heads and threadedshafts. Accordingly, the compression screw can be driven through theplate fixation hole and into the underlying bone until the head appliesa compression force against the bone plate toward the underlying bone.Another common bone screw used in such applications is generallyreferred to as a locking screw. Locking screws have threaded heads andthreaded shafts. Accordingly, the locking screw can be driven throughthe plate fixation hole and into the underlying bone until the headthreadedly mates with the bone plate in the fixation hole. Thus, thehead of the locking screw does not apply a compressive force against thebone plate toward the underlying bone.

Conventionally, locking screws were inserted through the screw holealong the central screw hole axis in order to ensure that the threadedscrew head mates with the plate in the threaded fixation hole. Recently,however, bone plates have been developed having threaded fixation holesthat are configured to receive locking screws at different trajectorieswithin a range of trajectories whereby the bone plate threadedly mateswith the locking screw head in the threaded hole. While bone plateshaving such holes, commonly referred to as variable angle holes, haveproved to be satisfactory for their intended purpose, improved variableangle holes are nevertheless desired.

SUMMARY

In accordance with one embodiment, a bone plate defines an inner surfaceconfigured to face bone, and an outer surface opposite the innersurface. The bone plate further includes an internal surface thatextends from the outer surface to the inner surface. The internalsurface defines a fixation hole that extends from the outer surface tothe inner surface along a central hole axis and is sized to receive ashaft of a bone anchor that extends out with respect to a threaded headof the bone anchor along a central anchor axis. The bone plate furtherincludes at least one thread that extends from the internal surface intothe fixation hole. The bone plate further defines a plurality ofrecesses that extend into the internal surface along a radially outwarddirection away from the central hole axis so as to interrupt the atleast one thread and divide the at least one thread into a plurality ofcolumns of thread segments. The recesses extend in a direction definedfrom the inner surface to the outer surface. The at least one thread isconfigured to threadedly mate with the threaded head while the boneanchor is inserted into the fixation hole such that the central anchoraxis is oriented at a first orientation with respect to the central holeaxis, and the at least one thread is further configured to threadedlymate with the threaded head when the bone anchor is inserted into thefixation hole such that the central anchor axis is oriented at a secondorientation with respect to the central hole axis that is different thanthe first orientation.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description, isbetter understood when read in conjunction with the appended drawings.For the purpose of illustrating the reconstruction device and relatedmethod thereof, there is shown in the drawings exemplary embodiments, inwhich like reference numerals correspond to like reference numeralsthroughout. The reconstruction device and related methods are notlimited to the specific embodiments and methods disclosed, and referenceis made to the claims for that purpose.

FIG. 1 is a perspective view of a bone fixation system constructed inaccordance with one embodiment, including a bone plate and a pluralityof fixation members that attach the bone plate to an underlying bone;

FIG. 2A is a perspective view of the bone plate illustrated in FIG. 1,constructed in accordance with one embodiment;

FIG. 2B is a perspective view of a bone plate constructed in accordancewith another embodiment;

FIG. 2C is a perspective view of a bone plate constructed in accordancewith yet one embodiment;

FIG. 3A is a perspective view of a portion of the bone plate illustratedin FIG. 1, showing a variable angle locking hole;

FIG. 3B is another perspective view of a portion of the bone plateillustrated in FIG. 3A;

FIG. 4 is a top plan view of the portion of the bone plate illustratedin FIG. 3A;

FIG. 5 is a sectional side elevation view of the portion of the boneplate illustrated in FIG. 4, taken along line 5-5;

FIG. 6 is a sectional side elevation view of the portion of the boneplate illustrated in FIG. 4, taken along line 6-6;

FIG. 7 is a sectional side elevation view of the portion of the boneplate illustrated in FIG. 3A, shown with a bone anchor threadedly matedto the bone plate inside the variable angle locking hole at a firstorientation;

FIG. 8 is a sectional side elevation view of the portion of the boneplate illustrated in FIG. 7, shown with a bone anchor threadedly matedto the bone plate inside the variable angle locking hole, and orientedat a second orientation different than the first orientation;

FIG. 9A is a perspective view of the portion of the bone plateillustrated in FIG. 4, but shown in accordance with an alternativeembodiment;

FIG. 9B is a sectional perspective view of the portion of the bone plateillustrated in FIG. 9A; and

FIG. 9C is a sectional perspective view similar to FIG. 9B, but showingthe bone plate constructed in accordance with an alternative embodiment.

DETAILED DESCRIPTION

Referring initially to FIG. 1, a bone fixation system 20 is configuredto be implanted onto bone 22 so as to stabilize a first bone segment 24with respect to a second bone segment 26 that is separated from thefirst bone segment 24 by a defect 28. In one example, the first bonesegment 24 can be defined by the diaphysis of the bone, while the secondbone segment 26 can be defined by the metaphysis of the bone. It shouldbe appreciated, however, that the first and second bone segments 24 and26 can be defined by any region of the bone 22 as desired. Further, thebone 22 can be any bone in the human or animal anatomy suitable for boneplate fixation. Further still, while the bone 22 is illustrated havingfirst and second bone segments 24 and 26, it is appreciated that thebone 22 can include any number of defects or bone fragments as desiredthat are configured for fixation using the bone fixation system 20. Forinstance, the diaphysis of the bone can include a plurality of bonefragments.

The bone fixation system 20 can include a bone plate 30 and a pluralityof bone anchors 32 that are configured to fix the bone plate 30 to theunderlying bone 22, and in particular to each of the first and secondbone segments 24 and 26. The bone anchors 32 include a head 33 and ashaft 35 that extends out with respect to the head 33 along a centralanchor axis 53. The shaft 35 can extend directly from the head, or canextend from a neck that is disposed between the head 33 and the shaft35. The shaft 35 can be threaded, such that the bone anchor 32 isconfigured as a bone screw 37 whose shaft 35 extends out relative to thehead 33 along the central anchor axis 53, which can also be referred toas a central screw axis. The threaded shaft 35 can be configured tothreadedly purchase in the underlying bone 22. For instance, one or moreup to all of the bone screw 37 can be configured as a cortical screwwhose threaded shaft 35 is designed and configured to threadedly mate tocortical bone. Alternatively or additionally, one or more of the bonescrews 37 can be configured as a cancellous screw whose threaded shaft35 is designed and configured to threadedly mate to cancellous bone. Itis appreciated that cancellous bone screws have threads that have agreater pitch than threads of cortical bone screws. Further, the threadsof cancellous bone screws typically extend out from the shaft of thebone screw a greater distance than the threads of cortical bone screws.

The bone plate 30 defines a bone plate body 31. The bone plate body 31,and thus the bone plate 30, defines an inner surface 34 configured toface the underlying bone 22, and an outer surface 36 that is oppositethe inner surface 34 along a transverse direction T. The bone plate 30further defines a plurality of fixation holes 38 that extend through thebone plate body 31 from the inner surface 34 to the outer surface 36. Inparticular, the bone plate body 31, and thus the bone plate 30, includesa plurality of internal surfaces 39 that extend from the outer surface36 to the inner surface 34 and defines a respective fixation hole 38that extends from the outer surface 36 to the inner surface 34 along acentral hole axis 45 (see FIGS. 7-8). The central hole axis 45 can beoriented along the transverse direction T. Thus, the central hole axis45 can be oriented normal to each of the inner surface 34 and the outersurface 36. It should be appreciated, of course, that the central holeaxis 45 can be oriented along any suitable direction with respect to theinner surface 34 and outer surface 36 as desired.

The fixation holes 38 are sized to receive the shaft 35 of a respectiveone of the bone screws 37. Thus, the bone screws 37 that extend throughfixation holes 38 are permanent bone screws, meaning that they remainafter completion of the surgical procedure. This is distinguished fromtemporary fixation holes that, for instance, can be configured toreceive temporary fixation members, such as Kirschner wires that areremoved prior to completion of the surgical procedure. In this regard,the fixation holes 38 can be referred to as permanent fixation holes.Accordingly, during operation, the shaft 35 of the bone screw 37 can beinserted through a respective one of the fixation holes 38 and into theunderlying bone 22. The bone screw 37 can then be rotated so as to causethe threaded shaft 35 to be driven into the underlying bone as thethreaded shaft 35 threadedly purchases with the underlying bone. Thethreaded shaft 35 can be driven into the underlying bone until the head33 engages the bone plate 30. One or more up to all of the bone screws37 can be configured as a compression screw whose head 33 is configuredto bear against the bone plate 30 so as to apply a compressive forceagainst the bone plate 30 toward the underlying bone 22 when the shaft35 is driven further into the underlying after the head 33 has contactedthe internal surface 39. The shaft 35 can be driven into the underlyingbone a sufficient distance until the desired compressive force has beenimparted onto the bone plate 30. The head 33 of the compression screw isoften unthreaded. Similarly, at least a portion up to an entirety of theinternal surface 39 can be unthreaded.

In another example, one or more up to all of the bone screw 37 can beconfigured as locking screws that are configured to lock to the boneplate 30. In particular, the head 33 can be externally threaded. Theinternal surface 39 can be similarly threaded so as to be configured tothreadedly mate with the threaded head 33. Accordingly, duringoperation, the shaft 35 can be inserted through the fixation hole 38 anddriven into the underlying bone as described above. In particular, whenthe bone screw 37 is a locking screw, rotation of the screw 37 causesthe threaded head to threadedly mate with the internal surface 39. As aresult, the screw head 33 fastens the bone plate 30 to the underlyingbone without applying a compressive force onto the bone plate 30 againstthe underlying bone. The bone plate 30 can be spaced from the underlyingbone when locked to the head 33. Alternatively, the bone plate 30 canabut the underlying bone when locked to the head 33. At least a portionof the internal surface 39 is typically tapered as it extends in anaxially inward direction from the outer surface 36 toward the innersurface 34. Thus, the internal surface 39 is configured to prevent thehead 33 from passing completely through the fixation hole 38. The head33 can be constructed in accordance with any embodiment as described inU.S. Pat. No. 8,574,268, the disclosure of which is hereby incorporatedby reference as if set forth in its entirety herein. Thus, it isappreciated that the head 33 can define at least one external threadthat is circumferentially continuous about the central anchor axis 53.It should be appreciated, however, that the head 33 can be alternativelyconstructed in any manner desired so as to threadedly mate with theinternal surface 39 as described herein.

Referring now to FIGS. 1 and 3A-3B, at least one of the fixation holes38 of the bone plate 30 is configured as a variable angle locking hole44 that is configured to threadedly mate with the bone screw 37 atdifferent orientations of the bone screw 37 with respect to the centralhole axis 45. That is, when the fixation hole 38 is configured as avariable angle locking hole 44, the bone plate body 31, and thus thebone plate 30, includes at least one thread 46 that projects out fromthe internal surface 39 into the fixation hole 38. Accordingly, theinternal surface 39 can define a threaded region 47 that carries the atleast one thread 46. The threaded region 47 can define at least aportion of the internal surface 39 up to an entirety of the internalsurface. In one example, the thread 46 can be monolithic with theinternal surface 39.

The bone screw 37 is configured to be inserted into the fixation hole 38such that the central anchor axis 53 is at one of a plurality oforientations with respect to the central hole axis 45 within a range oforientations at which the threaded head 33 is configured to threadedlymate with the at least one thread 46 in the fixation hole 38. Forinstance, the bone screw 37 is configured to be inserted into thefixation hole 38 such that the central anchor axis 53 is at one of aplurality of angles within a range of angles defined by the centralanchor axis 53 and the central hole axis 45 at which the threaded head33 is configured to threadedly mate with the at least one thread 46 inthe fixation hole 38. The range of angles can be from approximately zerodegrees to approximately 15 degrees. Thus, the range of angles candefine a cone of up to thirty degrees. Thus, it can be said that the atleast one thread 46 is configured to threadedly mate with the threadedscrew head 33 while the bone screw 37 is inserted into the fixation hole38 such that the central anchor axis 53 is oriented at a first anglewith respect to the central hole axis 45, and the at least one thread 46is further configured to threadedly mate with the threaded screw head 33when the bone screw 37 is inserted into the fixation hole 38 such thatthe central anchor axis 53 is oriented at a second angle with respect tothe central hole axis 45 that is different than the first angle. Atleast one or both of the first and second angles can be non-zero angles.Alternatively, the central anchor axis 53 can be coincident with thecentral hole axis 45 in one of the orientations in the range oforientations. The threads 46 and the threads of the head 33 are definedprior to insertion of the bone screw 37 into the variable angle lockinghole 44. That is, the internal surface 39 is not designed or configuredto cut threads into the bone screw head 33. Similarly, the bone screwhead 33 is not designed or configured to cut threads into the internalsurface 39. The variable angle locking hole 44 is described in moredetail below.

Referring now to FIGS. 2A-2C, the bone plate 30 can be configured in anysuitable manner as desired. In one example, the bone plate body 31, andthus the bone plate 30, can include a first plate portion 40 and asecond plate portion 42. In one example, the first plate portion 40 candefine a plate head portion 41 that is configured to overlie the secondbone segment 26, and the second plate portion 42 can be referred to as aplate shaft portion 43 that is configured to overlie the first bonesegment 24. Each of the plate head portion 41 and the plate shaftportion 43 can include at least one up to a plurality of bone fixationholes 38. Thus, bone anchors 32 that extend through respective fixationholes 38 of the plate head portion 41 can be driven into the metaphysisregion of the underlying bone, and bone anchors 32 that extend throughrespective fixation holes 38 of the plate shaft portion 43 can be driveninto the diaphysis region of the underlying bone. The metaphysis regioncan, for instance, be defined by the distal region of the radius bone.Any one or more up to all of the fixation holes 38 of the bone plate 30can be compression holes, locking holes, or variable angle locking holes44.

In one example, all of the fixation holes 38 in the first plate portion40 are variable angle locking holes 44. Further, in one example, all ofthe fixation holes 38 in the second plate portion 42 are compressionholes configured to receive cortical bone screws. Further, at least oneor more up to all of the compression holes can be configured as slotsthat are elongate along a central longitudinal axis of the bone plate toallow for positional flexibility of the bone screw received therein.Alternatively or additionally, at least one or more up to all of thecompression holes can have a circular cross-section so as to locate theposition of the bone screw received therein. As described above,however, it should be appreciated that the bone plate 30 can beconfigured to attach to any region or regions of any suitable bone inthe human or animal anatomy suitable for bone plate fixation.

Referring to FIGS. 2A-2C, the bone plate 30 is illustrated in accordancewith three non-limiting examples. In FIGS. 2A-2C, the bone plate 30defines a length that extends along a longitudinal direction L, a widththat is less than the length and extends along a lateral direction Athat is perpendicular to the longitudinal direction L, and a thicknessthat is less than both the length and the width and extends along thetransverse direction T that is perpendicular to each of the longitudinaldirection Land the lateral direction A. The bone plate 30 defines adistal direction from the plate shaft portion 43 to the plate headportion 41, and a proximal direction from the plate head portion 41 tothe plate shaft portion 43. The distal and proximal directions can beoriented along the longitudinal direction L. The bone plate 30illustrated in FIGS. 2A-2C has an outer perimeter 48 that is defined bythe plate shaft portion 43 and the plate head portion 41. Further, atleast a portion of the plate head portion 41 of the bone plate 30illustrated in FIGS. 2A-2C can be angled so as to extend outward as itextends in the distal direction away from the plate shaft portion 43.

Referring now to FIG. 2A in particular, the outer perimeter 48 can besubstantially Y-shaped. That is, the outer perimeter 48 can flare awayoutward as it extends along the distal direction from the plate shaftportion 43. Thus, the width of the bone plate 30 at the plate headportion 41 increases as it extends in the distal direction. The widthcan increase at a constant rate. Alternatively, the width can increaseat an increasing rate. Alternatively still, the width can increase at adecreasing rate. The plate head portion 41 can define a plurality offixation holes 38. One or more up to all of the fixation apertures inthe plate head portion 41 can be configured as variable angle lockingholes 44.

The fixation holes 38 of the head portion 41 can be arranged in a firstrow 50 a and a second row 50 b that is offset from the first row 50 a inthe proximal direction. The first row 50 a can contain a greater numberof fixation holes 38 than the second row 50 b. For instance, the firstrow 50 a can contain double the number of fixation apertures of thesecond row 50 b. In one example, the first row 50 a can include fourfixation holes 38, with first and second ones 38 a and 38 b of thefixation holes 38 of the first row 50 a disposed on a first side of alongitudinal centerline of the bone plate 30, and third and fourth ones38 c and 38 d of the fixation holes 38 of the first row 50 a disposed ona second side of the longitudinal centerline of the bone plate 30opposite the first side. The first one 38 a of the fixation holes 38 ofthe first row 50 a can be disposed laterally outward with respect to thesecond one 38 b of the fixation holes 38 of the first row 50 a.Similarly, the third one 38 c of the fixation holes 38 of the first row50 a can be disposed laterally outward with respect to the fourth one 38d of the fixation holes 38 of the first row 50 a. Further still, thecentral hole axis of the fourth one 38 d of the fixation holes 38 of thefirst row 50 a can be offset from the central hole axis of all otherones of the fixation holes 38 of the first row 50 a in the distaldirection. It should be appreciated, of course, that the first row 50 acan include any number of fixation holes 38 as desired, arranged asdesired. Further, the first and second rows 50 a and 50 b can be linearrows or can be curved as desired. In one example, the central hole axesof the fixation holes 38 of the fixed row lie on a nonlinear path.

The second row 50 b can include likewise include any number of fixationholes 38 as desired. In one example, the second row 50 b can includefirst and second ones 38 e and 38 f, respectively, of the fixation holes38. The central hole axes of the fixation holes 38 of the second row 50b are spaced from the central hole axes of the fixation holes 38 of thefirst row 50 a in the proximal direction. The first one 38 e of thefixation holes 38 of the second row 50 b can be disposed between thefirst and second ones 38 a and 38 b of the fixation holes 38 of thefirst row 50 a with respect to the lateral direction A. Similarly, thesecond one 38 f of the fixation holes 38 of the second row 50 b can bedisposed between the third and fourth ones 38 c and 38 d of the fixationholes 38 of the first row 50 a with respect to the lateral direction A.

The first and second ones 38 a and 38 b of the fixation holes 38 of thefirst row 50 a and the first one 38 e of the fixation holes 38 of thesecond row 50 b can be configured to receive bone screws that are driveninto one of the lunate fossa and the sigmoid notch. The third one 38 cof the fixation holes 38 of the first row 50 a can be configured toreceive a bone screw that is driven into the scaphoid fossa. The fourthone 38 d of the fixation holes 38 of the first row 50 a and the secondone 38 f of the fixation holes 38 of the second row 50 b can beconfigured to receive bone screws that are driven into one of thestyloid process. It is recognized that the central hole axes 45 of oneor more up to all of the fixation holes 38 a-38 f can be perpendicularto one or both of the bone plate surfaces 34 and 36, or nonperpendicularto one or both of the bone plate surfaces 34 and 36. In one example, therespective central hole axes 45 of the fixation holes 38 d and 38 f maydefine an angle with respect to one or both of the bone plate surfaces34 and 36 that is less than the angle defined by the central hole axesof the other fixation holes 38 a-38 c and 38 e and the one or both ofthe bone plate surfaces 34 and 36. Thus, the bone fixation holes 38 dand 38 f can be said to have increased angulation with respect to theother fixation holes 38 a-38 c and 38 e. The increased angulation canallow bone screws that are inserted through the fixation holes 38 d and38 f to be aligned with the styloid reach for fixation to the styloidreach.

Referring now to FIG. 2B in particular, the outer perimeter 48 can besubstantially T-shaped. That is, the outer perimeter 48 can defineopposed shoulders that flare out from the plate shaft portion 43 alongthe lateral direction A so as to define a proximal-most aspect of theplate head portion 41. The outer perimeter 48 can flare outward alongthe lateral direction A as it extends in the distal direction from theshoulders. Thus, the width of the bone plate 30 at the plate headportion 41 increases as it extends in the distal direction. The widthcan increase at a constant rate. Alternatively, the width can increaseat an increasing rate. Alternatively still, the width can increase at adecreasing rate. The plate head portion 41 can define a plurality offixation holes 38. One or more up to all of the fixation apertures inthe plate head portion 41 can be configured as variable angle lockingholes 44.

The fixation holes 38 of the head portion 41 can be arranged in a firstrow 50 a and a second row 50 b that is offset from the first row 50 a inthe proximal direction. The first row 50 a can contain a greater numberof fixation holes 38 than the second row 50 b. For instance, the firstrow 50 a can contain double the number of fixation apertures of thesecond row 50 b. In one example, the first row 50 a can include fourfixation holes 38, with first and second ones 38 a and 38 b of thefixation holes 38 of the first row 50 a disposed on a first side of alongitudinal centerline of the bone plate 30, and third and fourth ones38 c and 38 d of the fixation holes 38 of the first row 50 a disposed ona second side of the longitudinal centerline of the bone plate 30opposite the first side. The first one 38 a of the fixation holes 38 ofthe first row 50 a can be disposed laterally outward with respect to thesecond one 38 b of the fixation holes 38 of the first row 50 a.Similarly, the third one 38 c of the fixation holes 38 of the first row50 a can be disposed laterally outward with respect to the fourth one 38d of the fixation holes 38 of the first row 50 a. Further still, thecentral hole axis of the fourth one 38 d of the fixation holes 38 of thefirst row 50 a can be offset from the central hole axis of all otherones of the fixation holes 38 of the first row 50 a in the distaldirection. It should be appreciated, of course, that the first row 50 acan include any number of fixation holes 38 as desired, arranged asdesired. Further, the first and second rows 50 a and 50 b can be linearrows or can be curved as desired. In one example, the central hole axesof the fixation holes 38 of the fixed row lie on a nonlinear path.

The second row 50 b can include likewise include any number of fixationholes 38 as desired. In one example, the second row 50 b can includefirst and second ones 38 e and 38 f, respectively, of the fixation holes38. The central hole axes of the fixation holes 38 of the second row 50b are spaced from the central hole axes of the fixation holes 38 of thefirst row 50 a in the proximal direction. The first one 38 e of thefixation holes 38 of the second row 50 b can be disposed between thefirst and second ones 38 a and 38 b of the fixation holes 38 of thefirst row 50 a with respect to the lateral direction A. Similarly, thesecond one 38 f of the fixation holes 38 of the second row 50 b can bedisposed between the third and fourth ones 38 c and 38 d of the fixationholes 38 of the first row 50 a with respect to the lateral direction A.

The first and second ones 38 a and 38 b of the fixation holes 38 of thefirst row 50 a and the first one 38 e of the fixation holes 38 of thesecond row 50 b can be configured to receive bone screws that are driveninto one of the lunate fossa and the sigmoid notch. The third one 38 cof the fixation holes 38 of the first row 50 a can be configured toreceive a bone screw that is driven into the scaphoid fossa. The fourthone 38 d of the fixation holes 38 of the first row 50 a and the secondone 38 f of the fixation holes 38 of the second row 50 b can beconfigured to receive bone screws that are driven into one of thestyloid process. As described above with respect to FIG. 2A, it isrecognized that the central hole axes 45 of one or more up to all of thefixation holes 38 a-38 f can be perpendicular to one or both of the boneplate surfaces 34 and 36, or nonperpendicular to one or both of the boneplate surfaces 34 and 36. In one example, the respective central holeaxes 45 of the fixation holes 38 d and 38 f may define an angle withrespect to one or both of the bone plate surfaces 34 and 36 that is lessthan the angle defined by the central hole axes of the other fixationholes 38 a-38 c and 38 e and the one or both of the bone plate surfaces34 and 36. Thus, the bone fixation holes 38 d and 38 f can be said tohave increased angulation with respect to the other fixation holes 38a-38 c and 38 e. The increased angulation can allow bone screws that areinserted through the fixation holes 38 d and 38 f to be aligned with thestyloid reach for fixation to the styloid reach.

Referring now to FIG. 2C in particular, the outer perimeter 48 can beforked. That is, the plate head portion 41 can define first and secondarms 41 a and 41 b that extend away from the plate shaft portion 43 inthe distal direction, and are spaced from each other along the lateraldirection A. Respective first portions of the first and second arms 41 aand 41 b can flare away from each other along the lateral direction A asthey extend away from the plate shaft portion 43. Thus, the laterallyouter perimeter 48 at the first portion of the plate head portion 41 canflare out along the lateral direction A as it extends in the distaldirection. Respective second portions of the first and second arms 41 aand 41 b can flare toward from each other along the lateral direction Aas they extend away from the respective first portions. Thus, thelaterally outer perimeter 48 at the second portion of the plate headportion 41 can flare in along the lateral direction A as it extends inthe distal direction. The arms 41 a and 41 b can be disposed on oppositesides of the longitudinal centerline of the plate 30.

Each of the first and second arms 41 a and 41 b can include at least onefixation hole 38 such as a plurality of fixation holes 38. One or moreup to all of the fixation apertures in the plate head portion 41 can beconfigured as variable angle locking holes 44. The fixation holes 38 ofeach of the arms 41 a and 41 b can be arranged in a respective first row50 a and a second row 50 b that is offset from the first row 50 a in theproximal direction. The first row 50 a can be oriented substantiallyparallel to the outer perimeter 48 at the distal-most end of therespective arms 41 a and 41 b. For instance, the first row 50 a cancontain double the number of fixation apertures of the second row 50 b.In one example, the first row 50 a can include first and second ones 38a and 38 b of the fixation holes 38 of the first and second arms 41 aand 41 b, respectively. It should be appreciated, of course, that thefirst row 50 a can include any number of fixation holes 38 as desired,arranged as desired.

The second row 50 b of each of the first and second arms 41 a and 41 bcan include likewise include any number of fixation holes 38 as desired.In one example, the second row 50 b can include a respective one 38 c ofthe fixation holes 38. The central hole axes of the fixation hole 38 ofthe second row 50 b are spaced from the central hole axes of thefixation holes 38 of the first row 50 a in the proximal direction. Therespective one 38 c of the fixation holes 38 of the second row 50 b canbe disposed between the first and second ones 38 a and 38 b of thefixation holes 38 of the first row 50 a with respect to the lateraldirection A.

The first and second ones 38 a and 38 b of the fixation holes 38 of thefirst rows 50 a can be configured to receive bone screws that are driveninto the lunate fossa and sigmoid notch. Bone screws inserted into thehole 38 c can be aligned to be driven into the scaphoid fossa. Bonescrews inserted into the hole 38 d can be aligned to be driven into astyloid fragment. The fixation hole 38 a of the second row 50 b can beconfigured to receive a bone screw that is driven into the lunate fossaand sigmoid notch. Bone screws can be driven into hole 38 f of thesecond row to reach and support a styloid fragment.

The variable angle locking hole 44 will now be described, with initialreference to FIGS. 3A-6. In particular, and as described above, the boneplate 30 can include at least one up to a plurality of variable anglelocking holes 44. One of the locking holes 44 will now be described indetail, it being that the description is applicable to the other lockingholes of the bone plate 30. The bone plate 30 includes the internalsurface 39 that extends from the inner surface 34 to the outer surface36. The internal surface 39 defines the fixation hole 38 that similarlyextends through the bone plate body 31 from the outer surface to theinner surface along the central hole axis 45. In one example, thecentral hole axis 45 can extend along the transverse direction T. Itshould be appreciated, of course, that the central hole axis 45 can beoriented along any direction as desired, including a direction that isangularly offset with respect to the transverse direction T. Asdescribed above, the inner and outer surfaces 34 and 36 are oppositeeach other along the transverse direction T. Thus, in some examples, thetransverse direction T defined by the head portion 41 of the bone plate30 may be angularly offset with respect to the transverse direction Tdefined by the shaft portion 43 of the bone plate 30. In other examples,the transverse direction T can be constant along an entirety of thelength of the bone plate 30.

The fixation hole 38 is sized to receive the shaft 35 of the bone anchor32. In particular, the fixation hole 38 has a cross-sectional dimensionthat is defined from one location of the internal surface 39 to anotherradially opposite location of the internal surface 39 along a straightlinear direction that passes through the central hole axis 45 and isperpendicular to the central hole axis 45. In one example, thecross-sectional dimension defines a diameter of the internal surface 39.Thus, the internal surface 39 can extend along a circular path incross-section along a plane that is oriented normal to the central holeaxis 45. However, it is recognized that the internal surface 39 candefine any suitable geometry as desired. The cross-sectional dimensionis greater than the outer diameter of the at least one thread of thebone anchor shaft 35, such that the shaft 35 can travel through theinternal surface 39 so as to extend out from the inner surface 34 andinto the underlying bone.

The variable angle locking hole 44 can include the at least one thread46 that is configured to threadedly mate with the threaded head 33 ofthe bone anchor 32. In particular, the at least one thread 46 can extendfrom at least a portion of the internal surface 39 into the fixationhole 38 so as to define the threaded region 47. In one example, thethread 46 can be monolithic with the internal surface 39. Because the atleast one thread 46 is an internal at least one thread 46, the at leastone thread 46 defines a major diameter at the interface between the atleast one thread 46 and the internal surface 39. The at least one thread46 can extend out from the internal surface to a minor diameter that isradially inwardly spaced from the major diameter. The radially inwarddirection, as used herein, can be defined as a direction toward thecentral hole axis 45. A radially outward direction is opposite theradially inward direction. Thus, the radially outward direction, as usedherein, can be defined as a direction away from the central hole axis45. A direction normal to the central hole axis 45 can be said to beradial direction.

In one embodiment, the threaded region 47 extends along a portion of theaxial length of the internal surface 39. Alternatively, the threadedregion 47 can extend along an entirety of the axial length of theinternal surface 39. The at least one thread 46 can define a thread paththat is sloped with respect to a reference plane. The reference planecan be normal to the central hole axis 45. Thus, the reference plane canbe defined by the radial direction. The thread path can be defined bythe minor diameter of the at least one thread 46 that defines the threadcrest. In one example, the at least one thread 46 can be a helicalthread. Thus, the thread path can define a helix. Further, the at leastone thread 46 can define a single thread. Alternatively, the at leastone thread 46 can include multiple threads. For instance, the at leastone thread 46 can be configured as a double lead thread or alternativemultiple lead thread.

The internal surface 39 defines an axially inner end 52 that can extendto the inner surface 34. The axially inner end 52 can define an edgethat is shared by the inner surface 34. Alternatively, the axially innerend 52 can flare radially outward as it extends in the axially inwarddirection toward the inner surface 34. In one example, the axially innerend 52 flares radially outward as it extends in the axially inwarddirection. The axially inner end 52 can be defined by an undercut 56.Thus, the internal surface 39 can be defined by an undercut 56 thatflares radially outward to the axially inner surface 34. For instance,the undercut 56 can flare linearly to the axially inner surface 34.Thus, the axially inner end 52 of the internal surface 39 can define theundercut 56. Alternatively, at least a portion up to all of the undercut56 can be curved as it extends to the axially inner surface 34. Theundercut 56 can extend about an entirety of the perimeter of thevariable angle locking hole 44. The at least one thread 46 can extendradially inward from the undercut 56. Alternatively, the undercut 56 canbe devoid of threads, and can be substantially smooth. As will beappreciated from the description below, the undercut 56 can cause theinternal surface 39 to avoid contact with the shaft 35 at angles betweenthe central anchor axis 53 and the central hole axis 45 that would beprevented due to contact between the internal surface 39 and the shaft35 without the undercut 56. Thus, the undercut 56 can widen the range ofangles that are defined by the central anchor axis 53 and the centralhole axis 45 at which the threaded head 33 is configured to threadedlymate with the at least one thread 46 in the fixation hole 38.

The internal surface 39 defines an axially outer end 54 that is oppositethe axially inner end 54. The axially outer end 54 can extend to theouter surface 36. The axially outer end 54 can define an edge that isshared by the inner surface 34. Alternatively, the axially outer end 54can flare radially outward as it extends in an axially outward directionthat is opposite the axially inward direction, and thus in a directionfrom the inner surface 34 toward the outer surface 36. For instance, theaxially outer end 54 can flare radially outward as it extends in theoutward direction to the outer surface 36. It should be appreciated thatthe axially inward and axially outward directions can be oriented alongthe transverse direction T, or can define an angle with respect to thetransverse direction T. For instance, the internal surface 39 can betapered and extend along both the axially inward direction and theaxially outward direction.

The at least one thread 46 can extend from a first location 46 a to asecond location 46 b that is offset from the first location 46 a alongthe axially outward direction. The at least one thread terminates at thefirst location 46 a and the second location 46 b. The first location 46a can extend to the inner end 52 of the internal surface 39. Thus, thefirst location 46 a can extend to the inner surface 34. Alternatively,the first location 46 a can be offset from the inner surface 34 alongthe axially outward direction. The second location 46 a can extend tothe outer end 54 of the internal surface 39. Thus, the first location 46a can extend to a second region 49 of the internal surface 39 describedin more detail below. Alternatively, the second location 46 b can extendto the outer surface 36. Alternatively, the second location 46 b can beoffset from the outer surface 36 along the axially inward direction. Aswill be appreciated from the description below, the at least one thread46 defines at least one discontinuous segment between the first location46 a and the second location 46 b. The first location 46 a can bedefined by the inner end 52 of the internal surface 39. Thus, the firstlocation 46 a can extend inwardly to the inner surface 34.Alternatively, the first location 46 a can be offset from the innersurface 34 along the axially outward direction.

The plate body 31, and thus the plate 30, can define a step 58 thatprojects radially outward with respect to the threaded region 47 of theinternal surface 39. For instance, the step 58 can project radiallyoutward from the threaded region 47. The step 58 can be oriented along aplane that is normal to the central hole axis 45. Alternatively, thestep 58 can be sloped with respect to the plane that is normal to thecentral hole axis 45. Thus, it should be appreciated that the step 58can be oriented along any suitable direction as desired.

The internal surface 39 can define a second region 49 that extends fromthe step 58 to the axially outer surface 36. Thus, the axially outer end54 of the inner surface 39 can be defined by the second region 49. Thesecond region 49 can be tapered radially inwardly as it extends in theaxially inward direction. For instance, the second region 49 can betapered radially inwardly from the axially outer surface 36 to the step58. In one example, the second region 49 can be conical. The threadedregion 47 of the internal surface 39 can extend from the step 58 to theaxially inner surface 34. Alternatively, the threaded region 47 of theinternal surface 39 can extend from the step 58 to the undercut 56.Similarly, the columns 62 can extend from the step 58 to the axiallyinner surface 34. Alternatively, the columns can extend from the step 58to the undercut 56. The step 58 can define any surface area as desired.For instance, in one example, the surface area can be betweenapproximately 1.5 mm² and approximately 3 mm², such as approximately 2.1mm². The terms “approximate” and “substantially” as used herein withrespect to dimensions and shapes recognizes that manufacturingtolerances along with other factors, such as rounding, can causevariation in measurements and distances. Further, term “between” withrespect to ranges of dimensions is used herein to also include therespective dimensions.

The threaded region 47 can define any suitable height as desired. Theheight can be measured as an offset distance from the first location 46a of the at least one thread 46 to the second location 46 b of the atleast one thread 46 along the transverse direction T. Thus, the, theheight can be measured as an offset distance from the first location 46a of the at least one thread 46 to the second location 46 b of the atleast one thread 46 along a direction parallel to the central hole axis45. Accordingly, the height can be measured from the axially innersurface 34 to the step 58 along the transverse direction. If the boneplate 30 does not include the step 58 as illustrated in FIGS. 9A-9B, theheight can be measured from the inner surface 34 to the outer surface 36along the transverse direction T. In one example, the height of thethreaded region 47 can be between approximately 0.5 mm and approximately3 mm, such as between approximately 1 mm and approximately 2 mm, forinstance approximately 1.4 mm.

The second region 49 of the internal surface 39 can flare radiallyoutward from the step 58 to the axially outer surface 36. For instance,the second region 49 of the internal surface 39 can flare linearly alonga direction from the step to the axially outer surface 36.Alternatively, at least a portion up to all of the second region 49 ofthe internal surface 39 can be curved as it extends from the step 58 tothe axially outer surface 36. It should be appreciated that the threadedregion 47 of the internal surface 39 can be offset in the radiallyinward direction from the second region 49. That is, the threaded regioncan be disposed between the second region 49 and the central hole axis45 with respect to the radial direction. Further, at least a portion upto all of the threaded region 47 can be tapered radially inwardly alongits length as it extends in the axially inward direction. For instance,the threaded region 47 at each of the columns 62 can be conical from itsaxially outer end to the undercut 56, or alternatively can be conicalfrom its axially outer end to the axially inner surface 34 if theundercut 56 is not present. These areas can be referred to as taperedthreaded areas 51 of the threaded region 47, and thus of the internalsurface 39. The tapered threaded area 51 can define an axially outer endand an axially inner end. The axially outer end of the tapered threadedarea 51 can be defined by the step 58. Alternatively, if the bone plate30 does not include the step 58 as described below with respect to FIGS.9A-9B, then the axially outer end of the tapered threaded area 51 can bedefined by the axially outer surface 36. The axially inner end of thetapered threaded area 51 can be defined at the undercut 56.Alternatively, if the bone plate does not include the undercut 56, thenthe axially inner end of the tapered threaded area 51 can be defined bythe axially inner surface 34.

The conical shape of the second region 49 can be concentric with theconical shape of the threaded region of the internal surface 39. Theundercut 56 can extend out from the axially inner end of the radiallyinwardly tapered region of the internal surface 39. Further, theundercut 56 can include a portion of the at least one thread 46, andthus can define a portion of the threaded region 47. Alternatively, theundercut 56 can be devoid of threads. In one example, one or both of thestep 58 and the second region 49 of the internal surface 39 can bedevoid of threads designed to purchase with the threaded head 33 of thebone anchor 32. Thus, the fixation hole 38 can be configured to receivethe head of a compression screw, such that the head of the compressionscrew abuts the second region 49 and applies a compression force to thebone plate that urges the bone plate toward, for instance against, theunderlying bone as the compression screw is driven into the underlyingbone. One or both of the step 58 and the second region 49 of theinternal surface 39 can be said to be substantially smooth. The secondregion 49 at the step 58 can define any diameter as desired. In oneexample, the diameter of the second region at the step 58 can be in therange of approximately 2.5 mm and approximately 5 mm, for instance,between approximately 3 mm and approximately 4 mm, such as betweenapproximately 3.5 mm and approximately 4 mm, and in one example can beapproximately 3.7 mm. The diameter of the second region 49 at the stepcan also be referred to as an outer diameter of the step 58.

With continuing reference to FIGS. 3A-6, the plate body 31, and thus thebone plate 30, can define a plurality of (e.g., at least two) recesses60 that divide at least a portion of the threaded region 47 into aplurality of (e.g., at least two) columns 62. In particular, therecesses divide the at least one thread 46 into a plurality of columns62 of thread segments 64 that are described in more detail below.Opposed pairs of the columns 62 can be disposed radially opposite eachother through the central hole axis 45. At least a portion up to anentirety of each of the recesses 60 can extend through the threadedregion 47 at least to the internal surface 39 along the radially outwarddirection away from the central hole axis 45. For instance, at least aportion up to an entirety of each of the recesses can extend into theinternal surface 39 along the radially outward direction away from thecentral hole axis 45. Thus, the recesses 60 can further extend radiallyoutward through the at least one thread 46 that is carried by theinternal surface 39. Each of the recesses 60 terminates radially at arespective recessed surface 61 of the plate body 31. Thus, it can besaid that the recesses 60 can be at least partially or fully defined bythe recessed surface 61. It can further be said that each recessedsurface 61 defines a radial outer perimeter of the respective recesses60. The recessed surface 61 of each of the recesses 60 between adjacentones of the columns 62 can define any suitable surface area as desired.For instance, the surface area of the recessed surface 61 of each of therecesses 60 can be between approximately 0.5 mm² and approximately 4mm², such as between approximately 1 mm² and approximately 3 mm², and inone example can be approximately 1.9 mm².

The recesses 60 can have a radial depth sufficient such that therecessed surface 61 is recessed with respect to the internal surface 39along the radially outward direction. That is, the recessed surface 61can define a radial distance from the central hole axis 45 that isgreater than the radial distance from the central hole axis 45 to themajor diameter of the at least one thread 46. Further, an entirety ofthe recessed surface 61 can define a curvature along a plane that isoriented normal to the central hole axis 45 from a first end of therecessed surface 61 that adjoins the internal surface 39 to a second endof the recessed surface 61 that adjoins the internal surface 39. Thecurvature can be a constant curvature from the first end to the secondend. In one example, the recessed surface 61 extends along a circularpath along the plane that is oriented normal to the central hole axis45. The first and second ends of an entirety of the recessed surface 61at an entirety of the tapered threaded area 51 can diverge away fromeach other as they adjoin the internal surface 39. Further, a straightline that extends from the first end of the recessed surface to thesecond end of the recessed surface at the entirety of the taperedthreaded area 51 can define a chord of a circle that defines thecircular path of the recessed surface 61. The chord can be disposedbetween the center of the circle and the recessed surface 61. Thus, thefirst and second ends of the recessed surface can define acircumferential length that is less than or equal to (e.g., no morethan) 180 degrees of the circle that defines the circular path of therecessed surface 61 along a plane that is normal to the central holeaxis 45, along an entirety of the tapered threaded area 51. Thecircumferential length of the recessed surface 61 can decrease along theaxially outward direction. For instance, the recessed surface 61 candefine a minor arc along the plane from the first end of the recessedsurface 61 to the second end of the recessed surface 61, at an entiretyof the tapered threaded area 51.

In one example, the plate body 31 can include four recesses 60 that arecircumferentially spaced apart from each other. However, it isappreciated that the plate body 31 can include any number of recesses60, greater than one, as desired, so as to define the variable anglelocking hole 44 of the type described herein. Further, the respectiveconstant distance of the recessed surfaces of each of the recesses 60can be the same as each other. In this regard, each of the recesses 60can be substantially identical to each other. Further, the recesses 60can be circumferentially equidistantly spaced from each other about thecentral hole axis 45. Alternatively, the recesses 60 can becircumferentially spaced from each other a variable distance about thecentral hole axis 45. Similarly, the plate body 31 can include fourcolumns 62 of thread segments 64 that are circumferentially spaced apartfrom each other. However, it is appreciated that the plate body 31 caninclude any number of columns 62, greater than one, as desired, so as todefine the variable angle locking hole 44 of the type described herein.The columns 62 can be substantially identical to each other. Further,the columns 62 can be circumferentially equidistantly spaced from eachother about the central hole axis 45. Alternatively, the columns 62 canbe circumferentially spaced from each other a variable distance aboutthe central hole axis 45.

Adjacent ones of the columns 62 can be separated by a common one of therecesses 60. The adjacent ones of the columns 62 can be referred to ascircumferentially adjacent ones of the columns 62. The columns 62 andrecesses 60 can define circumferential centerlines that extend alongplanes that intersect the central hole axis 45. The circumferentialcenterlines of the columns can be circumferentially offset fromcircumferential centerlines of the recesses 60 by 45 degrees. Each ofthe columns 62 of the threaded region 47 includes a plurality of threadsegments 64. The thread segments 64 can be defined by the least onethread 46. The thread segments 64 of each of the columns 62 are offsetfrom each other along the transverse direction T. Further, the threadsegments 64 of each of the columns can define respective circumferentiallengths that decrease in the axially inward direction. The threadsegments 64 of each of the columns 62 can be discontinuous with respectto the thread segments 64 of the other ones of the columns 62 at therecesses 60. Thus, each of the recesses 60 interrupts the at least onethread 46 and divides the at least one thread 46 into the correspondingplurality of thread segments 64. Each column 62 can include a pluralityof the thread segments 64. Each column 62 can be tapered radiallyinwardly as it extends in the axially inward direction. Thus, thethreaded region 47 of the internal surface 39 at each of the columns 62can lie on a conical surface.

The thread segments 64 of each of the columns 62 can thus becircumferentially offset from the thread segments 64 of the other onesof the columns 62. Further, adjacent ones of the circumferentiallyspaced thread segments 64 can be separated by a common one of therecesses 60. Thus at least one or more of the thread segments 64 up toall of the thread segments 64 are aligned with at least one other of thethread segments 64 of an adjacent one of the columns 62 along the threadpath. For instance, at least one or more of the thread segments 64 up toall of the thread segments 64 are aligned with at least one other of thethread segments 64 of an adjacent one of the columns 62 along a helicalpath. In one example, each of a plurality of the thread segments 64 of arespective one of the columns 62 is aligned along a thread path with 1)a first one the thread segments 64 of a first other one of the columns62 that is adjacent the respective one of the columns 62 along a firstcircumferential direction, and 2) a second one the thread segments 64 ofa second other one of the columns 62 that is adjacent the respective oneof the columns 62 along a second circumferential direction that isopposite the first circumferential direction. Thus, the respective oneof the columns 62 is disposed circumferentially between the first otherone of the columns and the second other one of the columns. Further, thethread segments 64 of the respective one of the columns is disposedbetween the first one of the thread segments 64 and the second one ofthe thread segments 64 with respect to the transverse direction.

Each of the columns 62 can define a circumferential length in arespective plane oriented normal to the central hole axis 45. Thecircumferential length of each of the columns 62 can decrease in theradially inward direction. The thread segments 64 of each of the columns62 are offset from each other along the transverse direction T. Further,each of the thread segments 64 defines first and secondcircumferentially opposed terminal ends. Each of the thread segments 64defines a respective circumferential length from the firstcircumferentially terminal end to the second circumferentially terminalend. The circumferential lengths can be measured at the crests of thethread segments 64, which can be defined by the minor diameter. In oneexample, the circumferential lengths of the thread segments 64 decreasein the axially inward direction. In particular, the columns 62 define atleast three consecutive ones of the thread segments 64 whosecircumferential lengths decrease in the axially inward direction. It canthus also be said that the circumferential lengths of the at least threeconsecutive ones of the thread segments 64 increase in the axiallyoutward direction. Thus, the axially outermost one of the threadsegments 64 of each of the columns has a circumferential length greaterthan the axially innermost one of the thread segments 64 of each of thecolumns. The undercut 56 can be devoid of threads and smooth.Alternatively, the undercut 56 can define at least one thread segment 64that is consecutive with an axially innermost one of the thread segments64 of the each of the columns 62 along the thread path.

The recesses 60 further extend in a direction defined from the axiallyinner surface 34 toward the outer surface 36. In one example, each ofthe recesses 60 can extend from a respective axially first or innerterminal end to a respective opposed axially second or outer terminalend. The inner terminal end can be disposed at the axially inner surface34. Alternatively or additionally, depending on the size of the undercut56, the inner terminal end can be disposed at the undercut 56. Theundercut 56 can be localized at a location aligned with the columns 62so as to not extend circumferentially beyond the columns 62.Alternatively, the undercut 56 can extend about the entire perimeter ofthe variable angle locking hole 44. The outer terminal end can be spacedaxially inward from the axially outer surface 36. Accordingly, theaxially outer surface 36 can define an opening 29 of the variable anglelocking hole 44. The opening 29 thus has a continuous outer perimeterthat is defined by the axially outer surface 36 of the bone plate 30.Further, an entirety of the recessed surfaces 61 of each of the recesses60 can be offset from the outer perimeter of the opening in the radiallyinward direction, that is toward the central hole axis 45. Thus, theouter perimeter of the opening 29 can define a circle. It should beappreciated, however, that the outer perimeter of the opening 29 candefine any suitable alternative shape as desired. It should beappreciated, of course, that the axially outer surface 36 at the opening29 can define any suitable alternative shape as desired. For instance,as illustrated in FIG. 9A-9B, the recesses 60 can extend through thebone plate body to the axially outer surface 36, such that the recessedsurfaces partially define the outer perimeter. Thus, the axially outersurface 36 at the opening 29 can be defined by both the internal surface39 and the recessed surfaces 61. The axially outer surface 36 at theopening 29 at locations defined by the internal surface 39 can beconcave to the central hole axis 45 and defined by a first curvature,and the axially outer surface 36 at the opening 29 at locations definedby the recessed surfaces 61 can be concave to the central hole axis 45and defined by a second curvature that is greater than the firstcurvature.

Further, the outer terminal end can be disposed between the axiallyinner surface 34 and the axially outer surface 36. For instance, theouter terminal end of the recesses 60 can be disposed in the threadedregion 47. Thus, a portion of the at least one thread can be disposedbetween the second terminal end of the recess 60 and the axially outersurface 36 of the bone plate body 31. Further, the step 58 can bedisposed between the outer terminal end of the recesses 60 and theaxially outer surface 36 with respect to the transverse direction T.Accordingly, the internal surface 39 at the step 58 can define aconstant curvature along its length. The constant curvature can, forinstance, be circular. The internal surface 39 at the step 58 can defineany circumferential length as desired. In one example, thecircumferential length of the internal surface 39 at the step 58 can bein the range of approximately 5 mm and approximately 15 mm, forinstance, between approximately 10 mm and approximately 11 mm, such asapproximately 10.4 mm. The circumferential length of the internalsurface 39 at the step 58 can also be referred to as an innercircumference of the step 58.

In one example, at least a portion of the at least one thread 46 has acontinuous region 63 in which the at least one thread 46 extendscontinuously along at least one revolution about the central hole axis45. In one example, the at least one thread 46 can extend continuouslyalong a plurality of revolutions about the central hole axis 45. Thecontinuous region 63 can lie on the same thread path as the threadsegments 64. The continuous region 63 can be disposed between the outerterminal ends of the recesses 60 and the axially outer surface 36 of thebone plate 30. For instance, the continuous region 63 can extend fromone of the columns 62, and in particular from the axially outermostthread segment of the one of the columns 62. The continuous region 63can further extend to the axially outer surface 36 or to a location thatis offset from the axially outer surface 36 in the axially inwarddirection.

Thus, the outer terminal ends of the recesses 60 can be offset from theaxially outer surface 36 in the axially inward direction a distance thatis at least equal to or greater than the pitch of the at least onethread 46. In particular, the continuous region 63 can be disposedbetween the recesses 60 and the axially outer surface 36 with respect tothe transverse direction T. The continuous region 63 is positioned so asto purchase with the threaded head 33 of the bone anchor 32 when thebone anchor 32 is oriented such that the angle defined by the centralanchor axis 53 and the hole axis 45 are within the range of angles inwhich the threaded head 33 is configured to threadedly mate with the atleast one thread 46 in the fixation hole 38. In particular, the threadedhead is configured to thrededly mate with at least a portion of thecontinuous region 63 of the at least one thread 46 when the bone anchor32 is oriented such that the angle defined by the central anchor axis 53and the hole axis 45 are within the range of angles.

The recesses 60 can be oriented in any direction as desired. Forinstance, the recesses 60 can each be oriented along the transversedirection T. Accordingly, in one example, the recessed surface 61 ofeach of the recesses 60 can be spaced from the central hole axis 45 arespective constant distance along its length from the inner terminalend to the outer terminal end. Because the internal surface 39 can betapered radially inward as it extends in the axially inward direction,and because the recesses 60 are oriented along the transverse directionT from their inner terminal end to their outer terminal end, the radialdepth of the recesses 60 can decrease as the recesses 60 extend in theaxially outward direction. Further, the length of the recessed surface61 along a respective plane oriented normal to the central hole axis 45can decrease in the radially outward direction at the tapered threadedarea 51.

It should be similarly appreciated that the length of each of thecolumns 62 a respective plane oriented normal to the central hole axis45 can decrease in the radially inward direction. The tapered threadedarea 51 between its axially outer end and its axially inner end candefine any suitable surface area as desired. For instance, the surfacearea defined by the tapered threaded area 51 can be betweenapproximately 4.5 mm2 and approximately 9 mm2, such as betweenapproximately 5 mm² and approximately 8 mm², for instance betweenapproximately 6 mm² and approximately 7 mm², such as approximately 6.8mm². In one example, the plate body 31 can define an interface betweenthe axially inner end of the tapered threaded area 51 and the undercut56. The interface can have any suitable length as desired. For instance,the length of the interface can be between approximately 0.2 mm andapproximately 0.9 mm, such as between approximately 0.3 mm andapproximately 0.7 mm, such as approximately 0.5 mm.

Fabrication of the bone plate 30 can include the step of creating athrough-hole through the bone plate body 31 from the axially outersurface 36 to the axially inner surface 34. The creating step can, forinstance, include the step of creating the through-hole through the boneplate body 31 so as to define an interior surface of the plate body 31.The through-hole can be created such that the interior surface of thebone plate body 31 tapers radially inward toward the central hole axis45 as it extends in the axially inward direction, as described above.The creating step can, in one example, include the step of drilling thethrough-hole through the bone plate body 31. The drilling step can beperformed in a single step, or in multiple steps of creating athrough-hole, and then defining the through-hole to have a conicalshape. Further, the drilling step can include the step of creating acounterbore so as to define the step 58 and the corresponding secondregion 49 as described above. However, as recognized from thedescription below, the bone plate can be devoid of the step 58, suchthat the variable angle locking hole includes the threaded region 47 andnot the second region 49. Accordingly, the internal surface 39 candefine a constant taper from the axially outer surface 36 to theundercut 56, or to the axially inner surface 34 if the bone plate 30does not include the undercut. The method can further include the stepof creating the undercut 56 at the axially inner surface 34. Theundercut 56 can be created during the step of creating the through-hole,or after the through-hole has been created.

Next, the method can include the step of cutting the at least one thread46 into the interior surface so as to define the internal surface 39 andthe at least one thread 46. It should be appreciated that the minordiameter of the at least one thread 46 can be defined by the crest ofthe at least one thread 46, and the major diameter of the at least onethread can be defined by the internal surface 39. The thread can definea height from the minor diameter to the major diameter along its length.In one example, the height can be constant along at least a plurality ofrevolutions of the at least one thread 46 about the central hole axis45. Thus, the minor diameter of the thread can lie on a conicalgeometric shape. In another example, the height can increase or decreasealong the length of the at least one thread 46 as the at least onethread 46 extends in the axially inward direction. The method canfurther include the step of creating the recesses 60 in the internalsurface 39. The step of creating the recesses 60 can similarly createthe columns 62. Thus, the step of creating the recesses 60 can beperformed after the at least one thread is formed 46. Alternatively, thestep of creating the recesses 60 can be performed prior to forming theat least one thread 46. The recesses 60 can be created in the interiorsurface to define the columns 62, and the at least one thread 46 canthen be created in the columns 62 so as to define the interior surface39 and the at least one thread. Because the recessed surfaces 61 arecurved along an entirety of their length along a plane oriented normalto the central hole axis 45, the step of creating the recesses 60 can beachieved by drilling into the bone plate 30 along at least a portion ofthe internal surface 39. Thus, each of the recesses 60 defines acircumferential end that is open at the internal surface 39. In oneexample, each of the recesses 60 can be drilled into the axially innersurface 34 along the axially inward direction, such that the inner endof the recesses 60 have a radial depth that decreases as the recesses 60extend in the axially outward direction. The decreasing radial depth canbe due to the conical shape of the internal surface 39. The radial depthof the recesses 60 can be selected so as to define the columns 62 ofthread segments 64 as described above.

It is recognized that, due to the conical shape of the internal surface39, that the step of drilling the recesses 60 can also remove materialfrom the at least one thread 46 at a location axially outward from theouter terminal end of the recesses 60. In particular, material of thebone plate body 31 can be removed from the at least one thread 46 butdoes not extend radially through the at least one thread 46 so as tointerrupt the major diameter and extend into the internal surface 39.Thus, the at least one thread 46 can be said to be circumferentiallycontinuous with an increased minor diameter. The minor diameter at leastone thread 46 can thus include a plurality of sections having increaseddimensions that are aligned with the respective plurality of recesses 60along the transverse direction T. Nevertheless, because the majordiameter of the at least one thread 46 is uninterrupted at a locationaxially outward of the recesses, the at least one thread can be referredto as continuous with sections of increased minor diameter. Locations ofthe at least one whereby the major diameter of the at least one thread46 is interrupted can be referred to herein as thread segments 64 of oneof the columns 62. Locations of the at least one thread whereby themajor diameter is continuous and the minor diameter is increased can bereferred to herein as a circumferentially continuous portion of the atleast one thread that at least partially defines the continuous region63. The locations of the at least one thread having an increased minordiameter can be circumferentially continuous with locations of the atleast one thread having an uninterrupted minor diameter so as to definethe continuous region 63 that extends circumferentially at least onerevolution about the central hole axis 45. Further, the increaseddimensions of the minor diameters can decrease as in the axially outwarddirection due to the tapered, for instance, conical, profile of theminor diameter.

The bone plate body 31 can define a height along the transversedirection T from the axially inner surface 34 to the axially innermostend of the continuous region 63. The height can be any suitable heightas desired. In one example, the height can be between approximately 1.3mm and approximately 3 mm, including between approximately 1.75 mm and2.5 mm, such as approximately 2.25 mm. This height can also be said todefine the height of the recesses 60 along the transverse direction T.This height can also be said to define the height of the columns 62.

A method of bone fixation using the bone fixation system 20 will now bedescribed with further reference to FIGS. 7-8. In particular, the boneplate 30 is brought into proximity with the underlying bone. Forinstance, the axially inner surface 34 can be brought into contact withthe underlying bone, or can be spaced from the underlying bone. Aplurality of bone anchors can be inserted through respective bonefixation holes 38 of the bone plate 30 so as to fix the bone plate 30 tothe underlying bone at opposite locations of a bone defect of theunderlying bone. The method of fixing the bone plate 30 to theunderlying bone through the variable angle locking holes 44 includes thestep of inserting the shaft 35 of the bone anchor 32 through thefixation hole 38, which can be configured as the variable angle lockinghole 44, and into the underlying bone. The bone anchor 32 can be rotatedabout the central anchor axis 53 so as to drive the shaft 35 into theunderlying bone. As the bone anchor 32 is being driven into the bone,the central anchor axis 53 can define any suitable angle with respect tothe central hole axis 45 within a range of angles. The range of anglescan extend from 0 degrees to approximately 15 degrees as defined by thecentral anchor axis 53 and the central hole axis 45 in any directionabout the central hole axis 45, that is along the full 360 degreecircumference about the central hole axis 45. The range of angles can beachieved when bone screw fixation instrumentation, such as a drillguide, is also inserted into the fixation hole 38. The range of anglesof the central hole axis 45 with respect to the central anchor axis 53can define a cone about the central hole axis 45. Thus, the central holeaxis 45 can define the axis of the cone.

Continuing rotation of the bone anchor 32 while the angle defined by thecentral anchor axis 53 and the central hole axis 45 is in the range ofangles causes the threaded head 33 to advance into the variable anglelocking hole 44, such that the threaded head 33 threadedly mates withthe at least one thread 46 of the variable angle locking hole 44. Forinstance, a portion of the threaded head 33 can threadedly mate with thecontinuous region 63 of the at least one thread 46 alone or incombination with at least one or more of the columns 62 of threadsegments 64 up to all of the columns 62 of thread segments 64. Thus, thevariable angle locking hole 44 is configured to provide increasedsurface area contact with the head 33 of the bone anchor 32 with respectto conventional variable angle locking holes, thereby increasing thereliability of the threaded purchase between the bone plate and the boneanchor 32. It is recognized that different angles between the centralanchor axis 53 and the central hole axis 45 will cause the threaded head33 to threadedly purchase with different locations of the at least onethread 46 with respect to the transverse direction T.

Without being bound by theory, it is believed that the recesses 60assist in the ability of the bone anchor 32 to angulate with respect tothe central hole axis 45 within the range of angles while threadedlypurchasing with the at least one thread 46. Further, without being boundby theory, it is believed that the ability of the threaded head 33 tothreadedly purchase with both the columns 62 of thread segments 64 andwith the continuous region 63 of the at least one thread 46 can providemore reliable fixation than conventional variable angle locking holes.However, as will be appreciated from the description below, it isenvisioned that the continuous region 63 can be removed while providingadequate fixation by threadedly mating the threaded head 33 with thecolumns 62 of thread segments 64.

Referring now to FIGS. 9A-9B, it is recognized that the plate 30 can beconstructed in accordance with numerous examples, some of which havebeen described above. In one example, the bone plate can be devoid ofthe step 58 and the second region 49 of the internal surface 39.Accordingly, the surface that previously defined the step 58 of the boneplate 30 can define the axially outer surface 36. Thus, the threadedregion 47 can extend from the axially outer surface 36 to the axiallyinner surface 34. The tapered threaded area 51 of the threaded region 47can extend from the axially outer surface 36 to the undercut 56.Alternatively, for instance if the bone plate 30 does not include theundercut 56, the tapered threaded area 51 of the threaded region 47 canextend from the axially outer surface 36 to the axially inner surface34. In one example, the continuous region 63 of the at least one thread46 can extend from the columns 62 to the axially outer surface 36. Thus,the axially outer end 54 of the inner surface 39 can be defined by thecontinuous region 63.

Without being bound by theory, it is believed that removing the secondregion 49 such that the step 58 defines the axially outer surface 36allows the bone plate 30 to have a decreased height with respect toconventional variable angle bone plates while exhibiting increasedpurchase between the threaded screw head 33 and the bone plate 30 in thevariable angle locking hole 44. Thus, in one example, the height of thebone plate 30 from the axially inner surface 34 to the axially outersurface 36 along the transverse direction T can be between approximately0.5 mm and approximately 3 mm, such as between approximately 1 mm andapproximately 2 mm, for instance approximately 1.4 mm.

As noted below, it is believed that the bone plate 30 can achievesuperior fixation to the bone anchor head 33 while achieving a smallerbone plate height than conventional bone plates having variable anglelocking holes. However, without being bound by theory, it is furtherbelieved that the height of the bone plate 30 can be further reducedwhile achieving adequate fixation between the at least one thread 46 andthe threaded head 33. For instance, referring to FIG. 9C, in one examplethe at least one thread 46 can be devoid of the continuous region 63.Thus, the columns 62 extend from the axially outer surface 36 to theaxially inner surface 34. In this regard, it can be said that theentirety of the least one threaded region 47 is segmented into columns62 of thread segments 64. Thus, as described above, the tapered threadedarea 51 can extend from the axially outer surface 36 to the undercut 56.Alternatively, the tapered threaded area 51 can extend from the axiallyouter surface 36 to the axially inner surface 34 if the bone plate 30does not include the undercut 56. Further, an entirety of the taperedthreaded area 51 can be divided into columns 62 by the recesses 60.

In one example, the outer terminal ends of the recesses 60 can be offsetaxially inward with respect to the axially outer surface 36. However,the outer terminal ends of the recesses 60 are not offset from theaxially outer surface 36 a distance such that the at least one threadcan extend an entire revolution about the central hole axis 45 at alocation between the recesses and the axially outer surface. Thus, inone example, the offset distance can be less than the pitch of the atleast one thread 46. Alternatively, the recesses 60 can extend throughboth the axially inner surface 34 and the axially outer surface 36. Whenthe entirety of the at least one thread 46 defines the plurality ofcolumns 62, the internal surface 39 defines a surface area in the rangeof 4.0 to 6.5 mm², such as approximately 6.35 mm². Further, theelimination of the continuous region 63 of the at least one thread 46can allow the plate 30 to have a further reduced height from the axiallyinner surface 34 to the axially outer surface 36. In one example, theheight can be in the range of approximately 0.5 to approximately 1 mm,such as approximately 0.75 mm. It is appreciated that in FIG. 9C, anentirety of the surface area of the internal surface 39 is threaded withthe at least one thread 46, such that the entirety of the surface areaof the tapered threaded area 51 is available for threaded purchase withthe bone anchor 32 depending on the angle of the central anchor axis 53relative to the central hole axis 45.

The embodiments described in connection with the illustrated embodimentshave been presented by way of illustration, and the present invention istherefore not intended to be limited to the disclosed embodiments.Accordingly, those skilled in the art will realize that the invention isintended to encompass all modifications and alternative arrangementsincluded within the spirit and scope of the invention, as set forth bythe appended claims.

What is claimed:
 1. A bone plate comprising: an inner surface configuredto face bone, and an outer surface opposite the inner surface, aninternal surface that extends from the outer surface to the innersurface, the internal surface defining a fixation hole that extends fromthe outer surface to the inner surface along a central hole axis and issized to receive a shaft of a bone anchor that extends out with respectto a threaded head of the bone anchor along a central anchor axis, atleast one thread that extends from the internal surface into thefixation hole, the at least one thread having a continuous region inwhich the at least one thread extends continuously along at least onerevolution about the central hole axis; wherein the bone plate furtherdefines a plurality of recesses having at least a portion that extendsthrough the at least one thread at least to the internal surface in aradially outward direction away from the central hole axis so as tointerrupt the at least one thread and divide the at least one threadinto a plurality of columns of thread segments, the recesses furtherextending in an axially outward direction that extends from the innersurface to the outer surface, and wherein the at least one thread isconfigured to threadedly mate with the threaded head while the boneanchor is oriented at a first orientation with respect to the centralhole axis, and the at least one thread is further configured tothreadedly mate with the threaded head when the bone anchor is orientedat a second orientation angle with respect to the central anchor axisthat is different than the first orientation.
 2. The bone plate asrecited in claim 1, wherein the inner and outer surfaces are oppositeeach other along a transverse direction, and the continuous region isdisposed between the recesses and the outer surface and with respect tothe transverse direction.
 3. The bone plate as recited in claim 1,wherein the continuous region extends from an outermost one of thethread segments of one of the columns.
 4. The bone plate as recited inclaim 3, wherein the continuous region further extends to the outersurface.
 5. The bone plate as recited in claim 1, wherein the at leastone thread defines a minor diameter at the continuous region thatdefines sections of increased dimensions.
 6. The bone plate as recitedin claim 5, wherein the sections are aligned with respective ones of therecesses.
 7. The bone plate as recited in claim 1, wherein the innersurface is tapered in a radially inward direction as it extends in anaxially inward direction from the outer surface toward the innersurface, wherein the radially inward direction is opposite the radiallyoutward direction.
 8. The bone plate as recited in claim 1, wherein theat least one thread extends along a helical thread path.
 9. The boneplate as recited in claim 1, wherein the internal surface defines aradially outwardly extending step that separates the internal surfaceinto a threaded region and a second region that is disposed between thethreaded region and the outer surface.
 10. The bone plate as recited inclaim 9, wherein the second region is offset from the threaded region inthe radially outward direction.
 11. The bone plate as recited in claim9, wherein the second region is tapered in the radially inward directionas it extends in an axially inward direction from the outer surfacetoward the inner surface, the axially inward direction opposite theaxially outward direction.
 12. The bone plate as recited in claim 9,wherein the second region is unthreaded.
 13. The bone plate as recitedin claim 1, wherein the thread segments of each of the columns definerespective circumferential lengths that decrease in an axially inwarddirection from the outer surface toward the inner surface.
 14. The boneplate as recited in claim 1, wherein the recesses terminate at alocation that is spaced from the outer surface with respect to anaxially inward direction from the outer surface toward the innersurface.